Matthew Leaman recently published an article about the move to Polaris graphics cards on AmigaOS 4.x. He gave a good overview of why drivers for Polaris cards are needed and the work being done. That said, a picture is worth a thousand words, so I thought I'd give you a glimpse of the current driver in action (see above).
As you can see, the basics are up and running. It can output screens to the monitor; yes, UHD resolutions too. It's still sluggish because there's no graphics acceleration yet. However, the GPU and command processor are up and running, and work on graphics acceleration (blitter & compositing) should progress rapidly.
It's taken a lot of work to get to this point, including a few nasty surprises (which you'll hear about later). From here on it should be more straightforward, and I'm looking forward to having a fully functional driver up and running.